Porlock Salt Marsh, Exmoor, Somerset, UK. Dead trees in a salt marsh. The trees died because the soil became too saline for them to survive in. This salt marsh used to be agricultural land. A shingle beach (not seen) has protected the coast from the sea. The beach is being eroded away, which allows the sea to frequently inundate the land behind the beach. This has enabled the salt marsh to develop. Salt marshes form on coastal mud flats such as estuaries. This salt marsh is part of an important coastal geomorphological site, which has developed over many years.